1. Field of the Invention
The present invention relates to a magnetic memory and a method of its manufacture.
2. Description of a Related Art
In FIGS. 7(A)-(E) is shown a method of a magnetic memory of a related art. First, as shown in FIG. 7(A), a first Al conductive film 104 is formed on a SiO2 insulating film 102 and patterned. Then, a tunnel magnetoresistive (TMR) film 106 is deposited on the patterned conductive film 104, and patterned.
Next, as shown in FIG. 7(B), a layer insulating film 110 is formed on the insulating film 102 so as to cover the first conductive film 104 and the TMR film 106.
Next, as shown in FIG. 7(C), a photoresist is coated on the layer insulating film 110 so as to form a resist mask 120 having a pattern for contact.
Next, as shown in FIG. 7(D), the layer insulating film 110 is etched to form a contact hole so as to expose a part of the surface of the TMR film 106.
Next, as shown in FIG. 7(E), an Al wiring layer 108 is deposited. In this case, the wiring layer 108 is formed also on the inner face of the contact hole, so that the wiring on the layer insulating film 110 and an upper electrode of the TMR film 106 are connected electrically.
As described in the above, in such technique, the upper Al wiring layer is formed after the layer insulating film on the TMR film is removed by means of a dry etching that uses the patterned resist film as a mask, thereby establishing contact to the top part of the TMR film.
However, in the above process, the shape of the contact hole is determined by the patterning of the resist film. Moreover, a margin for mismatch between the TMR film and the contact hole is required to be secured in the process. As a result, there is a problem in that the contact between the top part of the TMR film and the upper wiring was not assured in a self-aligned manner, which was a stumbling block in advance toward refinement of the device.
Moreover, the thickness of the wiring layer in the cross-section of the contact hole is decreased due to incomplete filling of the contact hole in the formation process of the upper wiring layer. As a result, there are problems in that the sectional area of the upper wiring layer directly above the contact is reduced, and that the migration due to a writing current is increased.
Furthermore, in order to establish contact to the top part of the TMR film, it is necessary to remove the layer insulating film as deep as to the top part of the TMR film by means of plasma etching that uses the patterned resist film as a mask. As a result, there is a problem in that the yield of the TMR film is lowered due to the damage to the TMR film caused by the plasma etching.
In conjunction with the above description, a magnetic field detection element is disclosed in Japanese Patent Applications Laid Open, No. 2000-206220. In this citation, the magnetic field detection element is equipped with a perovskite type conductive oxide magnetic material electrode, a ferromagnetic metal electrode and an insulating film. The insulating film is disposed between the two electrodes, and detects a tunneling current. Moreover, the insulating film has a sufficient thickness which can shield off the exchange magnetic coupling between the two electrodes.
Furthermore, a tunnel magnetoresistive head is disclosed in Japanese Patent Applications Laid Open, No. 2001-34919. In this citation, the tunnel magnetoresistive head has a tunnel multilayer film obtained by laminating a tunnel barrier layer, a ferromagnetic free layer formed so as to sandwich the tunnel barrier layer, and a ferromagnetic pinned layer. In this head, a tunnel barrier layer and a nonmagnetic metal protective layer are formed sequentially on the ferromagnetic pinned layer. A side insulating layer is formed on both sides of the laminate that includes the ferromagnetic pinned layer, the tunnel barrier layer and the nonmagnetic metal protective layer. The surface of the nonmagnetic metal protective layer is cleaned, and a ferromagnetic free layer is formed so as to oppose the ferromagnetic pinned layer via the treated surface of the protective layer.
It is an object of the present invention to provide a magnetic memory and its method of manufacture by which the contact film between the TMR laminated film and the upper wiring can be formed in self-aligned fashion.
It is another object of the invention to provide a magnetic memory and its method of manufacture by which plasma damage to the TMR laminated film due to the etching of the layer insulating film can be eliminated.
It is another object of the invention to provide a magnetic memory and its method of manufacture by which reliability in a data writing current to the TMR laminated film can be enhanced.
It is another object of the invention to provide a magnetic memory and its method of manufacture by which the data writing current to the TMR laminated film can be reduced.
It is another object of the invention to provide a magnetic memory and its method of manufacture by which the line width of the wiring and the space between the wirings can be reduced so as to achieve the high density of the device.
According to a viewpoint of the present invention, the magnetic memory is equipped with a TMR laminated film formed on a first conductive film, and a second conductive film, formed on the TMR laminated film, having the same plane shape as the TMR laminated film.
Here, in the magnetic memory of this invention, the second conductive film has a flat surface. Moreover, the magnetic memory according to this invention may further be equipped with a first insulating film, formed so as to surround the TMR laminated film and the second conductive film, having a flat surface with the same height as the surface of the second conductive film, and a third conductive film, formed on the first insulating film, electrically connected to the second conductive film.
Moreover, from another viewpoint of this invention, the magnetic memory is equipped with a plurality of transistors formed in a matrix form on a substrate, first layer insulating films formed so as to cover the plurality of the transistors, a plurality of first conductive films formed on the plurality of transistors so as to expose only their top faces from the first layer insulating films, where respective films of the plurality of the first layer insulating films are connected to either one of the drain and the source of a plurality of the transistors of the corresponding columns, a plurality of magnetic memory elements formed on respective films of the plurality of the first layer insulating films, where respective elements of the plurality of the magnetic memory elements have TMR laminated films sandwiched between the corresponding films of the plurality of the first layer insulating films and the second conductive film, a second layer insulating film formed on the first layer insulating films with the same height as the height of the uppermost layer film so as to cover the plurality of the first layer insulating films, and so as to expose the top faces of the uppermost layer films of the plurality of the magnetic memory elements, and a plurality of third layer insulating films formed on the second layer insulating film, where respective films of the plurality of the third layer insulating films are connected electrically to the uppermost layer films of respective columns of the plurality of the magnetic memory elements.
From another viewpoint of the invention, the manufacturing method of the magnetic memory is equipped with a first step of laminating sequentially a first conductive layer, a TMR laminated layer, a second conductive layer and a soft magnetic layer on a first insulating film, a second step of forming a first hard mask by patterning the soft magnetic layer and the second conductive layer, a third step of forming a first conductive film by patterning the TMR laminated layer and the first conductive layer using the first hard mask, a fourth step of forming a soft magnetic film and a second conductive film as a second hard mask by patterning the patterned soft magnetic layer and the patterned second conductive layer, a fifth step of forming a TMR laminated film by patterning the patterned TMR laminated layer using the second hard mask, a sixth step of forming a second insulating film on the first insulating film so as to cover the first conductive film, the TMR laminated film, the second conductive film and the soft magnetic film, a seventh step of removing the second insulating film to the extent that the top face of the soft magnetic film is exposed, and an eighth step of forming a third conductive film on the second insulating film after removal so as to be connected electrically with the soft magnetic film.
From another viewpoint of the invention, the manufacturing method of the magnetic memory is equipped with a first step of laminating sequentially a TMR laminated layer and a conductive layer on a first conductive film, a second step of forming a second conductive film as a hard mask by patterning the conductive layer, a third step of forming a TMR laminated film by patterning the TMR laminated layer using the hard mask, a fourth step of forming an insulating film on the first conductive film so as to cover the first conductive film, the TMR laminated film and the second conductive film, a fifth step of removing the insulating film to the extent that the upper face of the second conductive film is exposed, and a sixth step of forming a third conductive film on the insulating film after the removal so as to connect it electrically to the second conductive film.
Moreover, from another viewpoint of the invention, the manufacturing method of the magnetic memory is equipped with a first step of laminating a TMR laminated layer, a conductive layer and a soft magnetic layer on a first conductive film, a second step of forming a soft magnetic film and a second conductive film as a hard mask by patterning the soft magnetic layer and the conductive layer, a third step of forming a TMR laminated film by patterning the TMR laminated layer, a fourth step of forming an insulating film on the first conductive film so as to cover the first conductive film, the TNR laminated film, the second conductive film and the soft magnetic film, a fifth step of removing the insulating film to the extent that the top face of the soft magnetic film is exposed, and a sixth step of forming a third conductive film on the insulating film after removal so as to connect it electrically to the soft magnetic film.
Moreover, from another viewpoint of the invention, the manufacturing method of the magnetic memory is equipped with a first step of sequentially laminating a TMR laminated layer and a conductive layer on a first conductive film, a second step of forming a second conductive film as a hard mask by patterning the conductive layer, and a third step of forming a TMR laminated film, with its topmost layer being the second conductive film, by patterning the TMR laminated layer.
As described in the above, in the present invention, the shape machining (milling process or etching process) of a tunnel magnetoresistive element (TMR laminated film) is carried out using a hard mask. In this way, the TMR laminated film can be formed in self-aligned fashion. Moreover, the thickness of the hard mask is set to be approximately equal to the thickness of the layer insulating film formed after the shape machining, and the contact to the upper part of the TMR laminated film is established through exposure of the hard mask by CMP. As a result, the contact can be established easily with high accuracy even if a refinement in the TMR laminated film is advanced. In addition, since the conventional method of etching the layer insulating film by means of a plasma is done away with, it is possible to eliminate the damage to the TMR laminated film by the plasma. Moreover, since the wiring above the TMR laminated film is formed on a plane, stability of the writing current and reliability of the wiring can be enhanced. Besides, it is possible to reduce the current required for writing by inserting a soft magnetic film between the upper wiring and the TMR laminated film.